This invention relates to magnetic recording mediums such as magnetic tapes, magnetic disks and the like and more particularly, to coating-type magnetic recording mediums which comprise ascorbic esters in or on a magnetic layer.
With so-called coating-type magnetic recording mediums which meet a recent demand for high recording density, a magnetic paint comprising very fine magnetic particles and a resin binder is applied onto a non-magnetic support to provide a magnetic layer thereon. In order to reduce a spacing loss, the magnetic layer has very good smoothness on the surface thereof.
This eventually leads to a great substantial contact area relative to sliding members, resulting in a great coefficient of friction. This will, in turn, cause a magnetic head portion to become high in temperature and thus, oxidation is more liable to occur, with the attendant problem that a substantial spacing loss results, with a lowering of output.
This usually results from a "brown stain phenomenon" wherein the head portion undergoes discoloration. The reason why such a brown stain takes place has never been discussed in detail yet, and it is considered that the stain is one caused by oxidation of the head or by deposition of an oxidized binder of a magnetic tape.
More particularly, it has been simulated that under high-speed sliding conditions with magnetic heads, a temperature at the friction point between the head and the medium reaches several hundred degrees centigrade or over. It is considered that at such high temperatures, the binder is oxidized or a material for the head may be oxidized, thereby bringing about an increase in leveling down quantity and eventual clogging of the head.
In the field of magnetic recording mediums, the durability degrades owing to the shortage in capability of additives used, particularly, lubricants. In other words, these additives cannot suppress the brown stain phenomenon based on the discoloration of a head portion. Thus, practical performances including an increase of a level-down quantity and a head-clogging defect are not satisfactory.